My nylon tent (good quality EMS brand) lasted fine, except I started storing it in the attic. Bad idea, the high heat (or variable temps) caused all of the seam seals to separate, eliminating the water proofing for the rain fly and other parts. All tents now stored in the basement (up off the floor).

How long of an exposure before UV degradation becomes an issue for nylon? I know my tents are not out of storage & at the campsite nearly as much as I would like, so I don't see UV as a big issue.